1. Field of the Invention
The present invention relates generally to a method and module for synthesizing image-sensing signals, and more particularly to a module which utilizes a single Analogy/Digital (AD) converter to receive and deal with two groups of image signals outputted from two image-sensing elements, and a method for synthesizing image signals outputted from two image-sensing elements.
2. The Related Art
Please refer to FIG. 13 and FIG. 14 that show the solution of a kind of high speed two-sided scanner. This solution adopts two independent image-sensing element I and image-sensing element II which acquires the image signals of double sides of a page separately, and matches a corresponding AD converter for each image-sensing element, namely image-sensing element I matches AD converter I, and image-sensing element II matches AD converter II, therefore, the AD converter I and AD converter II receive analogy optical signals outputted from the image-sensing element I and image-sensing element II respectively, and convert the analogy optical signals into the digital signals, then transfer the digital signals to the scanner controller for further handling. Image-sensing elements utilized in this solution may be Charged-Coupled Device (CCD), Complementary Metal-Oxide Semiconductor (CMOS) or Contact Image Sensor (CIS), etc.
Therein, the image-sensing elements that are controlled by the driving signal (include Clock signal PHi1, PHi2, Reset signal RS and Clamp signal CP) outputted from the drive circuit send a pixel in series into the AD converter during a clock cycle T.
However, this solution must adopt extremely complicated scanner controller that is very expensive to deal with two groups of digital image signals at the same time. This causes the cost of the high-speed two-sided scanner at present to remain high, therefore the high speed two-sided scanner is difficult to popularize.
Besides, the resolution of scanners generally is 600 dpi (dot/inch) or more, however, the resolution of 300 dpi is accurate enough for scanners to scan figures of texts and documents. For a scanner of 600 dpi resolution, the output time of the image pixels in every inch of the scanned object will last 600 clock cycles. Therefore, if the demanded resolution for processing is 300 dpi, each side of the scanning page just need to output half pixels of the 600 dpi resolution, namely the total output pixels of two sides scanning from the image-sensing element is equal to the amount of output pixels of single side scanning. It is possible to use the present common scanner controller to realize two-sided scanning functions.